Grant: Strategic Projects Supplemental Competition

Phosphorus (P) levels in many lakes on the Precambrian Shield in Ontario have declined over recent decades, and may be approaching levels that are limiting to aquatic life. We hypothesize that P exports from drainage basins in this region have decreased over recent decades as a result of soil acidification and/or climatic change. Decades of high inputs of acid deposition have caused soils to acidify in many Precambrian Shield basins, and greater iron and aluminium availability in acidified soils may be enhancing P retention in the drainage basin. In addition, climate warming may result in lower P inputs to lakes by decreasing the amount of runoff available to leach P from soils. The objectives of this proposal are to investigate the roles of soil acidification and hydroclimatic change in determining long-term patterns in lake P across the Precambrian Shield region of Ontario. Improved understanding of the relationships between processes occuring in the drainage basin and P inputs to lakes is required for environmental policy pertaining to residential development and recreational fishing in Precambrian Shield lakes.